This invention relates to a radio pager receiver that can receive message signals carrying messages and destined to the pager receiver.
A radio pager receiver becomes widespread which can provide not only an indication of a call received by the pager receiver but also visual displays of a message on a display unit, such as a liquid crystal display (LCD).
For this purpose, the pager receiver comprises a message processor activated by main electric power supplied from a main battery through a manually operable power source switch. The message processor is for processing the message signals into the respective messages and administration data for use in administrating the messages. In this event, the message processor processes the message signals to have the administration data related to one another in accordance with a logical relationship. More specifically, the message processor makes the logical relationship comprise message linkage information. For each of the messages, the message linkage information is indicative of a message order in which the message signals are processed into the respective messages.
A memory is coupled to the message processor and is activated by the main electric power. The memory has a message area for storing the messages and an additional area for storing the administration data. The messages are stored in the message area while the administration data are stored in the additional area in correspondence to the respective messages. In this manner, the message and the additional areas are used in memorizing the messages and the administration data as a content of the memory.
The memory is typically a random access memory (RAM). Therefore, the content of the memory is erased when the memory is deactivated by disconnection of the main electric power. The disconnection of the main electric power occurs when the power source switch is put into an off state. The disconnection also occurs when the main battery is detached from the pager receiver in order to exchange the main battery.
With a view to preventing such erasure of the content of the memory, a memory backup method is generally used wherein the memory is backed up by backup electric power supplied from a backup battery even when the memory is deactivated by disconnection of the main electric power.
In the manner known in the art, the content of the memory is not always correctly kept or retained in the memory when the memory is again activated after once deactivated. Therefore, a backup test is generally carried out when the memory is again activated after once deactivated. The backup test is for judging whether or not the content of the memory is correctly kept when the memory is again activated after once deactivated. This makes it possible to confirm the content of the memory by making the display unit display the content of the memory when the memory and the message processor are activated after once deactivated.
A conventional radio pager receiver capable of executing the backup test is disclosed in U.S. Pat. No. 4,779,091, by Takashi Ohyagi and Toshihiro Mori for assignment to the instant assignee. The Ohyagi et al patent application corresponds to European Patent Application No. 87101273.8 filed Jan. 30, 1987, Canadian Patent Application No. 528,529 filed Jan. 30, 1987, Australian Patent Application No. 68168/1987 filed Jan. 30, 1987, and Korean Patent Application No. 780/1987 filed Jan. 31, 1987.
In the conventional radio pager receiver, a specific datum is preliminarily written in a prescribed part of the additional area of the memory. The specific datum is, for example, a datum of two bytes consisting of "10101010" and "01010101" wherein each digit of one of the two bytes has one of logic "1" and "0" levels when a corresponding digit of another of the two bytes has the other of the logic "1" and "0" levels. In order to check whether or not the memory backup is correctly executed, the message processor judges whether or not the specific datum of two bytes is correctly kept in the prescribed part of the additional area of the memory when the memory is again activated after once deactivated.
Inasmuch as the specific datum of two bytes must be preliminarily written in the prescribed part of the additional area of the memory, it is defective in that the conventional radio pager receiver is incapable of readily checking whether or not memory backup is correct.
As an alternative of the specific datum of two bytes, it is possible to use another specific datum of one byte. In this event, a one-byte datum "00000000" would result when the specific datum of one byte is added to all data stored in the message area and the additional area collectively as stored data. It is therefore necessary to renew the specific datum of one byte so as to always provide the one-byte datum "00000000" whenever the stored data are renewed in the message and the additional areas. Such renewing operation of the specific datum of one byte is not only complicated but also time consuming. This is because it is necessary to check all stored data in the message and the additional areas whenever the stored data are renewed in the message and the additional areas.
At any rate, the conventional radio pager receiver is incapable of readily checking whether or not the memory backup is correct.